1. Field of the Invention
The invention relates generally to an optical scanning module and, more particularly, to an objective lens anti-shock adjustment device arranged in the optical scanning module to mount an objective lens.
2. Description of the Related Art
A conventional flat bed type scanning apparatus comprises an optical scanning module that is capable of performing a forward and backward sliding movement under a transparent glass to scan a document placed on the transparent glass. The optical scanning module of the flat type scanning apparatus is usually driven by means of a motor and transmission elements.
Referring to FIG. 1, a schematic side view illustrates a conventional construction of an optical scanning module. An optical scanning module conventionally comprises a housing 170 in which are respectively arranged a light source 110, a reflective lens assembly 140, an objective lens 150, and an image sensor 160. The light source 110 projects a light on a document 120 that is placed on a transparent glass 130 to be scanned. The resulting light from the document 120 passes through the reflective lens assembly 140, composed of a plurality of reflective lenses (140a, 140b, 140c), is directed to the objective lens 150, and finally forms an image on the image sensor 160. The image sensor 160 may be, for example, a charge coupled device (CCD).
FIG. 2 is a perspective view that schematically illustrates an objective lens mounting device used to mount the objective lens 150 within the optical scanning module. FIG. 3 is a schematic view that particularly illustrates the mounting of the objective lens within the mounting device. As shown in FIG. 2, an objective lens mounting device 180 known in the prior art is traditionally formed with the housing 170 in a single body, and generally comprises a base to which is connected a hexagonal hollow tube 182 that receives the objective lens 150. The objective lens 150 can be slid along the axis of the hexagonal hollow tube 182 to adjust the depth of focus. Once the adequate depth of focus is obtained, a fixing screw locks the objective lens within the hexagonal hollow tube 182. As shown in FIG. 3, the objective lens 150 is thereby held via six contact points achieved through the six sides of the hexagonal tube 182.
As there are increasing demands for a scanning apparatus that has reduced dimensions, the useless portions of material of the objective lens 150 outside the image light path 152 accordingly have to be removed to reduce the size of the objective lens 150. FIG. 4 is a sectional view that shows the resulting section of an objective lens 150a modified according to the above requirement of dimensional reduction. As shown in FIG. 5, a disadvantage of the above dimensional reduction however is that the objective lens 150a may be subjected to a deviation from its correct horizontal orientation due to, for example, external shocks. As a result, the image light 152 does not entirely pass through the objective lens 150a, which negatively affects the image formation on the image sensor 160.
An aspect of the invention is therefore to provide an objective lens anti-shock adjustment device that enables the mounting of an objective lens and further protects the objective lens from external shocks.
Another aspect of the invention is to provide an objective lens anti-shock adjustment device that allows an optical adjustment of the objective lens according to different axes, and more particularly according to two translation axes for adjusting the depth of focus and the vertical positioning and one rotation axis for adjusting the horizontal orientation of the objective lens.
To accomplish the above and other objectives, the invention provides an objective lens anti-shock adjustment device that is arranged in an optical scanning module to mount an objective lens. The objective lens anti-shock adjustment device comprises a holder that is capable of fixedly holding the objective lens via at least a fastening element. The holder is mounted according to a flexible and adjustable manner in a casing by means of a plurality of resilient elements and a plurality of adjuster screws. The resilient elements connect the holder to the casing and the adjuster screws engage through the casing and abut against the holder opposite to the resilient elements in order to allow the adjustment of a vertical positioning and a horizontal orientation of the objective lens. The holder and the casing are provided with respective openings that expose a slot formed on the objective lens according to a direction perpendicular to the light path through the objective lens. By external engagement of a tool through the openings into the slot, the objective lens is slid in the holder in order to adjust the depth of focus.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.